Removing an operating system from the hard disk

You may find that you no longer need one of the operating
systems installed on your hard disk.
If you want to delete an operating system, use the
appropriate version of fdisk.
To delete a UNIX partition, you must use the UNIX system version of
fdisk.
To delete a DOS partition, use fdisk under DOS.
To delete an Extended
DOS partition, you must delete all logical drives on that
partition using fdisk.
Deleting the partition removes the contents of that partition
and leaves unallocated space.

You can then reallocate that space by either adding another
UNIX or DOS partition, or enlarging an existing partition.
Enlarging a partition requires reinstalling the operating system
and (for a UNIX partition) remaking the filesystem on
the partition using
divvy(ADM).